UK team grows cubic GaN on 3C-SiC on silicon
MOCVD technique offers promise of lower cost, more efficient LEDs
Anvil Semiconductors and the Cambridge Centre for GaN at the University of Cambridge have successfully grown cubic GaN on 3C-SiC on silicon wafers by MOCVD. The underlying 3C-SiC layers were produced by Anvil using its patented stress relief IP that enables growth of device quality SiC on 100mm diameter silicon wafers.
According to the researchers, the process can be migrated onto 150mm diameter wafers and potentially beyond without modification and is therefore suitable for large, industrial-scale applications.
The MOCVD growth trials at Cambridge, conducted under a project funded by Innovate UK, have resulted in single phase, cubic GaN. The layers, characterised by XRD, TEM, photoluminescence and AFM, show promise for LED applications.
The availability of cubic GaN has the potential to remove the strong internal electric fields which plague conventional green LEDs and which impair recombination and make it difficult to address high internal quantum efficiency (IQE).
Additionally, cubic GaN has a narrower bandgap and improved p-type electrical properties compared to the standard hexagonal GaN phase normally used for LEDs and therefore offers several advantages. The ability to produce cubic GaN from a readily commercialisable process on large diameter silicon wafers is clearly recognised as a key enabler for increasing the efficiency and reducing the cost of LED lighting.
"This is a very promising development and fits well with our current research activities to develop state of the art LEDs. It has the potential to overcome many of the challenges currently seen for green devices and could contribute significantly to the ongoing solid state lighting revolution," said Sir Colin Humphreys, Professor and Director of Research, Department of Materials Science and Metallurgy at University of Cambridge.
Jill Shaw, CEO of Anvil Semiconductors added: "This is a very exciting result which potentially opens up the LED market for our 3C-SiC on silicon material. We will certainly be looking for partners to help us take this opportunity forward".
The team intends to continue development to the point of fabricating sample LEDs before looking for an industry partner to help commercialise the technology.
Anvil Semiconductors, which is backed by Business Angels and early stage VCs, was established in August 2010 to develop SiC power devices for the power electronics industry. Anvil's approach to making SiC switches involves growing a thin layer of 3 step cubic SiC (3C-SiC) on silicon substrates sufficient to build the active power devices. In addition to the fundamental crystal growth expertise, Anvil has IP relating to resolving the problem of the stress which is inevitable when growing SiC on silicon and which to date has prevented the widespread adoption of this technology. The Anvil IP has been proven on 100mm diameter silicon wafers and can be readily migrated onto larger wafer diameters without modification.
The Cambridge Centre for GaN is part of the Department of Materials Science and Metallurgy in the University of Cambridge and is led by Sir Colin Humphreys. It has been actively involved in the development of GaN growth technologies for more than 15 years and is the leading group for GaN materials research in the UK.
Through its current activities the Group supplies epitaxial layers to many groups involved in GaN research both in the UK and internationally. It has experience in the growth of GaN layers on to Sapphire, bulk SiC, bulk GaN and large area silicon substrates and in 2011 the IP developed for GaN growth on silicon was acquired by Plessey Semiconductors, who are currently using this technology to manufacture LEDs commercially.
